[1] Univ London Imperial Coll Sci Technol & Med, Dept Biosurg & Surg Technol, Acad Surg Unit, St Marys Hosp, London W2 1NY, England
[2] E Surrey Hosp, Dept Upper Gastrointestinal Surg, Redhill, Surrey, England
[3] Queen Alexandra Hosp, Dept Gastroenterol, Portsmouth, Hants, England
[4] Univ Western Australia, Dept Gastroenterol, Fremantle Hosp, Fremantle, WA, Australia